I'm not convinced she owes them anything - they left their house set up as a cat trap, and it trapped a cat. I don't see that that is her fault.
So does every cat owner on this thread ensure that they lock their cat flap every single time they go on holiday or are away overnight?
The sad story about the pine marten upthread shows that animals will find any possible way in that they can, and I don't think you can blame the owner for not having a hermetically-sealed home. Letterboxes, drain pipes, air vents, tumble dryer outlets - all standard openings in a normal home.
Obviously, if it's a wild animal, then all damages will have to be covered by the home owner, as nobody owns it - and nobody ultimately feels devastated if it dies; but if it's an animal that somebody is supposed to love and be responsible for, why should they not pay?